`nix shell` puts `~/.nix-profile/bin` first in PATH

[wch]

On my Mac where I used the Determinate Systems installer, when I run nix shell, it puts ~/.nix-profile/bin as the first thing in the PATH, but this means that if there is a copy of a program installed there, it will be used instead of the program I want to use with nix shell.

For example, suppose you already have hello installed on your system.

❯ hello
Hello, world!

I have a hello flake at https://github.com/wch/nix-hello-demo that prints something slightly different:

❯ nix run github:wch/nix-hello-demo
Hello, World! This is a demo of a Nix flake.

However, when I use nix shell, and the run hello, it runs the regular version instead of my customized one.

# Mac with Determinate Systems installer
❯ nix shell github:wch/nix-hello-demo
❯ hello
Hello, world!

Note that this happens on my Mac, but not on my NixOS computer (where I didn't use the Determinate Systems installer). The behavior on NixOS is what I would expect on the Mac.

# NixOS (without Determinate Systems installer)
❯ nix shell github:wch/nix-hello-demo
❯ hello
Hello, World! This is a demo of a Nix flake.

On the Mac, in the nix shell the PATH is set so that /Users/winston/.nix-profile/bin:/nix/var/nix/profiles/default/bin: come first, before /nix/store/050vas2swsvr7sqrf75mkxwi851ycxcz-hello/bin. On the NixOS machine, those two paths are not put first.

I found that the PATH is being set by /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh. Is it intentional that those directories are put first even when nix shell is used?

[Hoverbear]

I was trying to reproduce this on an older Mac install I had and was not able to. I suspect it's related to something that changed in 0.15, perhaps related to the new Mac Nix hooks. I'm going to spend some more time investigating. Thank you for this report!

[Hoverbear]

I tested this again in 0.16.0 today and was able to confirm it. Noting you do need to nix profile install nixpkgs#hello before entering the nix shell to reproduce.

[Hoverbear]

I was able to reproduce this on an aarch64 Sonoma 14.3 using the installer from https://nixos.org/download as well as ours, in your issue you stated you also tried with the upstream installer, however it was when the upstream installer was pointing to 2.18 (I believe). I wonder if this is a Nix 2.19 issue.

~ % nix profile install nixpkgs#hello
~ % nix shell github:wch/nix-hello-demo
~ % hello
Hello, world!
~ % echo $PATH
/Users/user/.nix-profile/bin:/nix/var/nix/profiles/default/bin:/nix/store/050vas2swsvr7sqrf75mkxwi851ycxcz-hello/bin:/Users/user/.nix-profile/bin:/nix/var/nix/profiles/default/bin:...
~ % nix --version
nix (Nix) 2.19.3
~ % sw_vers
ProductName:            macOS
ProductVersion:         14.3
BuildVersion:           23D56

I was also able to reproduce this on a fresh Ubuntu VM using the upstream installer: